Re: Onto a potential relational manipulation language

On Dec 12, 1:29 pm, vadim..._at_gmail.com wrote:

> Next,
>
> (x v y) v z = z
>
> that is z contains a subset of attributes common to x and y. With
> these assumptions the projection

Typo, again! The correct condition is

((x v y) v z) ^ R00 = z

The implication

z ^ R00 = z &
((x v y) v z) ^ R00 = z
-> (x + y) v z = (x v y) v z.

is still a theorem in RL. Received on Fri Dec 12 2008 - 22:37:17 CET